Section 6: Terminal Anchor Joint Selection for Concrete Pavement

6.1 Terminal Joint Design Recommendation

Concrete experiences volume changes due to temperature and
moisture variations. Normally, concrete pavement is abutted to bridge
structures via approach slabs. To prevent damage to the bridge structures,
some form of system is installed at the bridge and pavement interface.
There were three systems in use at the department: expansion joint
system, wide-flange system, and anchor lug system.

The basic premise of the expansion joint system is that the
expansion joint width will be able to absorb any concrete pavement
expansion without transmitting the compression forces to the bridge structure.

The wide-flange system is similar to the expansion system,
except that the expansion joints exist under the wide flange and
are not seen from the pavement surface. One advantage is that, since
the joint is not exposed to the pavement surface, joint maintenance
is minimized.

An anchor lug system tries to contain the concrete movement
at the interface between bridge and pavement by providing five anchor
lugs.

The department has investigated the movements of CRCP near
bridges and the effectiveness of these three terminal systems in
Research project 0-6326, “Rational Use of Terminal Anchorages in Portland
Cement Concrete Pavements.”

The research data has shown that the anchor lug system is
not effective. The stresses generated in soil due to slab expansion
at lug walls are large enough to result in permanent deformations
in soils. The soil does not retract with the lug when the pavement
contracts. The permanent deformations result in voids between soil
and lug walls.

Field measurements have indicated that the base friction restrains
slab movements effectively. Using coarse-textured base such as HMA
might be the most effective tool to control slab movements. Simple
expansion joint systems or wide-flange systems are effective in
accommodating slab movements. Expansion joint systems should cost
less than wide-flange systems and attain comparable performance.

The use of anchor lug systems is no longer allowed, and the
standard TA(CP)-99 has been deleted. The transverse expansion joint
details at bridge approaches are shown in the concrete pavement standards.

Districts may develop a Special Specification to use the wide-flange
system.